Fuel cells, by the use of electrochemical reactions, serve as an energy source for mobile or stationary applications. They may offer lower emissions, higher energy and lower levels of noise and vibration as compared to alternative energy sources. A fuel cell may typically include a negative electrode (e.g., anode), a positive electrode (e.g., cathode) and a membrane between the anode and cathode.
While various membranes may be employed in the development of fuel cells, polymer electrolyte membranes or proton exchange membranes (PEMs) are currently important components of fuel cells. For example, high temperature (HT) PEMs which are operational at temperatures above 120° C. with no or low humidification, may exhibit beneficial properties such as anode tolerance to significant quantities of carbon monoxide poisoning, enhanced electrode kinetics, reduced cathode flooding, and efficient thermal management.
There are limitations, however, to the existing membranes used in fuel cells and their methods of production. For example, polymer proton conductors including perfluorosulfonic polymers such as Nafion®, which are widely used as a standard materials in low temperature PEM (e.g., perfluorosulfonic acid (PFSA) membrane, sulfonated PEM) fuel stacks due to their proton conductivity and stability, may be difficult to synthesize. The capital costs thus associated with producing some low temperature PEMs still remain high. Also, sulfonated PEMs may depend strongly on the amount of water the membranes contain and the temperature of exposure. Furthermore, membranes having free phosphoric acid (H3PO4) may exhibit acid leaching, thus resulting in decreased proton conductivity.
Therefore, a need exists to develop mechanically and thermally stable polymer electrolyte membranes exhibiting low acid leaching and high proton conductivity at high temperatures and low relative humidity.